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Published on: January 25, 2017
prM-reactive antibodies reveal a role for partially mature virions in dengue virus pathogenesis
Kimberly A Dowd1, Devika Sirohi2,3, Scott D Speer1
1Viral Pathogenesis Section, Laboratory of Viral Diseases, National Institutes of Health, Bethesda, MD 20892.
Abstract:
Cleavage of the flavivirus premembrane (prM) structural protein during maturation can be inefficient. The contribution of partially mature flavivirus virions that retain uncleaved prM to pathogenesis during primary infection is unknown. To investigate this question, we characterized the functional properties of newly-generated dengue virus (DENV) prM-reactive monoclonal antibodies (mAbs) in vitro and using a mouse model of DENV disease. Anti-prM mAbs neutralized DENV infection in a virion maturation state-dependent manner. Alanine scanning mutagenesis and cryoelectron microscopy of anti-prM mAbs in complex with immature DENV defined two modes of attachment to a single antigenic site. In vivo, passive transfer of intact anti-prM mAbs resulted in an antibody-dependent enhancement of disease. However, protection against DENV-induced lethality was observed when the transferred mAbs were genetically modified to inhibit their ability to interact with Fcγ receptors. These data establish that in addition to mature forms of the virus, partially mature infectious prM+ virions can also contribute to pathogenesis during primary DENV infections.
Insights
Partially mature dengue virus (DENV) with uncleaved prM protein contributes to disease. Anti-prM antibodies can enhance or protect against DENV infection depending on their Fc receptor interaction.
Area of Science:
- Virology
- Immunology
- Structural Biology
Background:
- Flavivirus premembrane (prM) protein cleavage is essential for virion maturation.
- Inefficient prM cleavage results in partially mature virions.
- The role of these partially mature virions in dengue virus (DENV) pathogenesis is not well understood.
Purpose of the Study:
- To investigate the contribution of partially mature DENV virions to pathogenesis during primary infection.
- To characterize the functional properties of DENV prM-reactive monoclonal antibodies (mAbs).
Main Methods:
- In vitro neutralization assays using DENV prM-reactive mAbs.
- Alanine scanning mutagenesis to identify antigenic sites.
- Cryoelectron microscopy to determine antibody-virion complex structures.
- In vivo studies using a mouse model of DENV disease, including passive antibody transfer.
Main Results:
- Anti-prM mAbs demonstrated neutralization in a virion maturation state-dependent manner.
- Two distinct modes of antibody attachment to a single antigenic site on immature DENV were identified.
- Intact anti-prM mAbs led to antibody-dependent enhancement of DENV disease in vivo.
- Genetically modified anti-prM mAbs, unable to interact with Fcγ receptors, provided protection against DENV-induced lethality.
Conclusions:
- Partially mature infectious prM+ virions contribute to DENV pathogenesis.
- Antibody interactions with Fcγ receptors influence the outcome of anti-prM antibody-mediated protection or enhancement.
- These findings highlight the complex role of virion maturation status in flavivirus infection and immunity.
